
import { Observable, Notification } from 'rxjs';
import { materialize as higherOrder } from 'rxjs/operators';

/**
 * Represents all of the notifications from the source Observable as `next`
 * emissions marked with their original types within {@link Notification}
 * objects.
 *
 * <span class="informal">Wraps `next`, `error` and `complete` emissions in
 * {@link Notification} objects, emitted as `next` on the output Observable.
 * </span>
 *
 * <img src="./img/materialize.png" width="100%">
 *
 * `materialize` returns an Observable that emits a `next` notification for each
 * `next`, `error`, or `complete` emission of the source Observable. When the
 * source Observable emits `complete`, the output Observable will emit `next` as
 * a Notification of type "complete", and then it will emit `complete` as well.
 * When the source Observable emits `error`, the output will emit `next` as a
 * Notification of type "error", and then `complete`.
 *
 * This operator is useful for producing metadata of the source Observable, to
 * be consumed as `next` emissions. Use it in conjunction with
 * {@link dematerialize}.
 *
 * @example <caption>Convert a faulty Observable to an Observable of Notifications</caption>
 * var letters = Rx.Observable.of('a', 'b', 13, 'd');
 * var upperCase = letters.map(x => x.toUpperCase());
 * var materialized = upperCase.materialize();
 * materialized.subscribe(x => console.log(x));
 *
 * // Results in the following:
 * // - Notification {kind: "N", value: "A", error: undefined, hasValue: true}
 * // - Notification {kind: "N", value: "B", error: undefined, hasValue: true}
 * // - Notification {kind: "E", value: undefined, error: TypeError:
 * //   x.toUpperCase is not a function at MapSubscriber.letters.map.x
 * //   [as project] (http://1…, hasValue: false}
 *
 * @see {@link Notification}
 * @see {@link dematerialize}
 *
 * @return {Observable<Notification<T>>} An Observable that emits
 * {@link Notification} objects that wrap the original emissions from the source
 * Observable with metadata.
 * @method materialize
 * @owner Observable
 */
export function materialize<T>(this: Observable<T>): Observable<Notification<T>> {
  return higherOrder()(this) as Observable<Notification<T>>;
}
